Cigarettes and Cigarette Filters Including Activated Carbon for Removing Nitric Oxide

ABSTRACT

Filters and cigarettes include an activated carbon sorbent capable of selectively removing nitric oxide from mainstream tobacco smoke. Methods for making cigarette filters and cigarettes using the activated carbon sorbent and methods for treating mainstream tobacco smoke produced by smoking a cigarette comprising the sorbent are also provided.

RELATED APPLICATIONS

This application is a U.S. divisional patent application of U.S. patentapplication Ser. No. 14/564,950, filed Dec. 9, 2014, which is a U.S.divisional patent application of U.S. patent application Ser. No.14/011,132, filed Aug. 27, 2013, now issued as U.S. Pat. No. 8,905,042on Dec. 9, 2014, which is a U.S. divisional patent application of U.S.patent application Ser. No. 11/305,338, filed Dec. 19, 2005, now issuedas U.S. Pat. No. 8,539,957 on Sep. 24, 2013, which claims priority under35 U.S.C. § 119(e) to U.S. Provisional Application No. 60/643,607entitled CIGARETTES AND CIGARETTE FILTERS INCLUDING ACTIVATED CARBON FORREMOVING NITRIC OXIDE and filed on Jan. 14, 2005, wherein the entirecontents of each is hereby incorporated by reference.

BACKGROUND

Absorbent and adsorbent materials have been suggested for incorporationinto smoking articles, such as cigarettes, for the purpose of removingconstituents from mainstream smoke.

SUMMARY

Cigarette filters, cigarettes including the cigarette filters, methodsfor making the cigarette filters and cigarettes, and methods forremoving gaseous constituents from gas streams, such as from mainstreamtobacco smoke, are provided.

In a preferred embodiment, the cigarette filter contains an activatedcarbon sorbent that has a pore structure effective to remove nitricoxide (i.e., NO) from mainstream tobacco smoke.

In a preferred embodiment, a majority of the pores of the activatedcarbon sorbent have a pore size of less than about 30 Å, e.g., fromabout 5 Å to about 20 Å, or from about 5 Å to about 10 Å.

In a preferred embodiment, the activated carbon sorbent contains poreshaving a D-R micropore volume of from about 0.2 cm³/g to about 1.0 cm³/gin the pore size range of from about 5 Å to about 10 Å.

In another preferred embodiment, the filter also contains a catalystcapable of catalyzing the reaction of nitric oxide to N₂ and O₂ and/orto NO₂.

In a preferred embodiment, the activated carbon sorbent is used toremove nitric oxide from a gas stream.

A preferred embodiment of a method of making a cigarette filtercomprises incorporating an activated carbon sorbent into a filter, atone or more parts of the filter.

A preferred embodiment of a method of making a cigarette comprisesplacing a paper wrapper around a tobacco column to form a tobacco rod,and attaching a cigarette filter including an activated carbon sorbentto the tobacco rod to form the cigarette.

A preferred embodiment of treating tobacco smoke comprises heating orlighting the cigarette to form smoke, and drawing the smoke through acigarette filter of the cigarette. An activated carbon sorbent providedin the cigarette removes nitric oxide from mainstream smoke.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a partially-broken away side view of a preferred embodiment ofa cigarette comprising a tobacco rod and a multi-component filter.

FIG. 2 is a partially-broken away side view of another preferredembodiment of a cigarette.

FIG. 3 shows the NO concentration (curve A) and the NO₂ concentration(curve B) versus time of an effluent gas using as-received porous carbonbeads, and the NO₂ concentration (curve C) versus time of an effluentgas using activated carbon beads, for an influent gas mixture containingNO.

FIG. 4 shows the % NO removal versus time for as-received carbon derivedfrom coconut shells (curve A) and treated carbon derived from coconutshells (curve B) of an effluent gas using an NO-containing gas mixtureas the influent.

FIG. 5 schematically illustrates a smoking test system used for testingcigarettes for NO removal efficiency.

FIG. 6 shows the % change of NO contained in a gas composition forconsecutive puffs using as-received carbon derived from coconut shellsand treated carbon derived from coconut shells.

FIG. 7 shows the % change of NO contained in a gas composition forconsecutive puffs using treated carbon derived from coconut shells.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Cigarette filters and cigarettes are provided that include an activatedcarbon sorbent capable of removing nitric oxide from mainstream tobaccosmoke. Methods of making the cigarette filters and cigarettes, as wellas methods of treating cigarette smoke using filters including theactivated carbon sorbent, are also described. Methods of removing nitricoxide from a gas stream are also described.

As used herein, the term “sorption” includes filtration by adsorptionand/or adsorption. Sorption encompasses interactions on the outersurface of the sorbent, as well as interactions within the pores andchannels of the sorbent. In other words, a “sorbent” is a substance thatcan condense or hold molecules of other substances on its surface,and/or can take up other substances, i.e., through penetration of theother substances into its inner structure, or into its pores.Accordingly, the term “sorbent” as used herein refers to an adsorbent,an absorbent, or a substance that can function as both an adsorbent andan absorbent.

As used herein, the term “remove” refers to adsorption and/or absorptionof at least some portion of at least one constituent of a gas stream,such as mainstream tobacco smoke. At least one constituent of a gasstream may be converted to another constituent by a catalytic reaction,which effectively also removes the constituent from the gas stream.

The term “mainstream smoke” includes the mixture of gases that pass downthe tobacco rod and issue through the filter end, i.e., the smoke thatissues or is drawn from the mouth end of a smoking article duringsmoking of the smoking article. Mainstream smoke contains air that isdrawn in through both the lit region of the smoking article and throughthe paper wrapper.

The activated carbon sorbent preferably has a pore structure that ismade up substantially of micropores or mesopores. As used herein, a“micropore” has a pore size of about 2 nm (20 Å) or less, and a“mesopore” has a pore size of from about 2 nm to about 50 nm (20 Å to500 Å). See, for example, Pure Appl. Chem., Vol. 73, No. 2, pp. 381-394(2001). The pore size of the activated carbon sorbent can be chosenbased on the selected constituent(s) that is/are desired to be removedfrom a gas stream, e.g., from mainstream tobacco smoke.

If desired, the activated carbon sorbent can be used in combination withone or more catalyst materials in a gas passage, e.g., in a cigarettefilter and/or cigarette, to enhance conversion of one or more selectedconstituents in the gas stream to another gaseous constituent. In apreferred embodiment, a catalyst material capable of catalyzing thereaction of nitric oxide to N₂ and O₂ and/or to NO₂ is provided in thecigarette filter. For example, the catalyst can be any suitabletransition metal catalyst, such as Fe₂O₃ and/or Fe₃O₄. The catalyst canbe nano-sized and/or micro-sized. The catalyst can be provided invarious components of a cigarette filter, e.g., on the activated carbonsorbent as a coating. Alternatively, the activated carbon sorbent andthe catalyst can be in the form of a physical mixture in the gaspassage.

The activated carbon sorbent is preferably incorporated in a traditionalcigarette or a non-traditional cigarette. For example, the activatedcarbon sorbent can be incorporated in a cigarette with or without hollowcores, fuel elements or other arrangements, or in non-traditionalcigarettes, such as cigarettes for electrical smoking systems describedin commonly-assigned U.S. Pat. Nos. 6,026,820; 5,988,176; 5,915,387;5,692,526; 5,692,525; 5,666,976 and 5,499,636, each of which isincorporated herein by reference in its entirety.

The activated carbon sorbent can be provided in gas passages, e.g., incigarettes, in various physical forms. For example, the activated carbonsorbent can be in the form of beads, fibers, monolithic bodies, granulesand/or a coating on a substrate. In a preferred embodiment, theactivated carbon sorbent is in the form of spherical beads to achieve adesired resistance-to-draw (RTD). The beads can typically have anaverage diameter of from about 0.2 mm to about 1 mm, with 0.3 mm to 0.5mm beads being preferred to achieve a desired RTD.

Monolithic bodies of activated carbon sorbent can have a cylindricalshape, as well as various other shapes that may include oval orpolygonal cross sectional shapes, sheet-like, spherical, honeycomb, orother monolithic shapes, and the like. The monolithic bodies can havedifferent sizes. For example, when used in monolithic form in acigarette filter, the activated carbon sorbent can be disc-shaped orcylindrical, and preferably has a length of from about 2 mm to about 20mm and a diameter slightly less than the diameter the filter portion ofthe cigarette.

In a preferred embodiment, the monolithic body is oriented in a gaspassage, such as a cigarette filter, so that the body extends lengthwisealong the length direction of the gas passage. Such orientation of thesorbent increases the length of the flow path through the sorbenttraveled by the gas, such as mainstream tobacco smoke, thus exposing thegas to an increased total surface area of pores. Accordingly, theremoval of nitric oxide from the gas stream by the sorbent can beincreased.

The activated carbon sorbent includes pores having pore sizes effectiveto remove nitric oxide from a gas stream, such as from mainstreamtobacco smoke. While not wishing to be bound to any particular theory,it is believed that the removal of NO from a gas stream by the sorbentinvolves the adsorption of NO by the surface through micropore filling.

The activated carbon sorbent can be produced by processing a suitablecarbonaceous material or carbon-yielding precursor. The activated carbonsorbent is preferably produced from carbon beads, or from natural orsynthetic organic materials, e.g., from coconut shells. Carbonaceousmaterials can include non-porous carbon and porous carbon. Porous carbonmaterials include materials, such as carbon molecular sieves.

Carbonaceous materials are subjected to an activation process to producean activated carbon sorbent having a desired pore structure. Porouscarbon materials are subjected to activation to modify the existing porestructure by forming additional pores and changing the existing poresize distribution.

The activation step utilizes any suitable oxygen-containing environment,which contains steam, carbon dioxide, oxygen or potassium hydroxidesolution, at an elevated temperature, e.g., from about 400° C. to about900° C. The environment can also contain other gases, such as nitrogen.These gases react with the carbon, resulting in a porous carbonstructure. Oxygen and nitrogen can also be chemically attached to thecarbon surface to enhance gas filtration selectivity based onchemisorption, i.e., the formation of a covalent bond.

In a preferred embodiment, the carbonaceous material is activated to adesired level of burn-off. The “burn-off” represents the weight loss(i.e., weight loss=initial weight−final weight) of the carbon thatoccurs during the activation process. As the level of burn-off isincreased, the carbon surface area increases. The BET (Brunauer, Emmettand Teller) surface area of the activated carbon sorbent is preferablyfrom about 1000 m²/g to about 3,000 m²/g, more preferably from about1000 m²/g to about 2,000 m²/g.

The Dubinin-Redushkevich (D-R) micropore volume of those pores of theactivated carbon sorbent that have a pore size of from about 5 Å toabout 10 Å is preferably from about 0.2 cm³/g to about 1.0 cm³/g, morepreferably from about 0.3 cm³/g to about 1.0 cm³/g. In a preferredembodiment, the activated carbon sorbent has a specific surface area offrom about 1000 m²/g to about 2,000 m²/g, and a D-R micropore volume ofthe pores that have a pore size of from about 5 Å to about 10 Å is fromabout 0.3 cm³/g to about 1.0 cm³/g.

During activation, burn-off is preferably controlled to control the poresize, pore surface area and pore volume of the activated carbon sorbent.At a given activation temperature, increasing the activation timeincreases the BET surface area and the pore volume/gram (i.e., D-R valuemicropore volume) of the activated material. In addition, increasing theactivation time can cause the growth of small pores, e.g., pores havinga size of from about 5 Å to about 10 Å into larger pores, e.g., poreshaving a size of from about 10 Å to about 20 Å. Accordingly, theactivation time is preferably controlled to control pore growth andprovide a desired pore size distribution.

In a preferred embodiment, following activation, the activated carbonsorbent contains pores that are larger than the molecule size of one ormore selected constituents of mainstream tobacco smoke that are targetedfor removal. Only those constituents of the gas stream, e.g., mainstreamtobacco smoke, that are small enough to enter into the pores of thesorbent can be adsorbed on the interior surface of the pores. Thus,constituents of the gas stream having sufficiently small molecularstructures are selectively removed by the sorbent, while largerconstituents, such as those that contribute to flavor in a cigarette,are not able to enter the pores and are substantially not removed fromthe gas stream by the sorbent.

As described above, the pore structure of the activated carbon sorbentcan be adjusted in the manufacturing process by controlling theactivation conditions. In a preferred embodiment, the activated carbonsorbent is processed to provide a pore size effective to selectivelyremove nitric oxide. Accordingly, the activated carbon sorbent includespores that are larger than the size of the nitric oxide molecule. In apreferred embodiment, the majority of the pores of the activated carbonsorbent have a size of less than about 30 Å, more preferably less thanabout 20 Å, and most preferably less than about 10 Å.

In a preferred embodiment, the activated carbon sorbent is incorporatedin the filter portion of a cigarette. In the filter portion, theactivated carbon sorbent is preferably incorporated in at least onespace and/or void.

The activated carbon sorbent also can be incorporated in the tobacco bedof a cigarette, such as in the tobacco rod.

The amount of the activated carbon sorbent provided in a cigarette canbe varied. For example, about 50 mg to about 200 mg of the activatedcarbon sorbent can typically be used in a cigarette to providesufficient filling and effective NO removal performance. More than 200mg of activated carbon sorbent can be used. However, such embodimentsmay have a shorter tobacco rod in order to maintain a certain cigarettelength. Increasing the amount of the sorbent in the filter can increasethe total amount of NO that can be removed from mainstream tobaccosmoke.

An exemplary embodiment of a method of making a cigarette filtercomprises incorporating an activated carbon sorbent into a cigarettefilter, wherein the activated carbon sorbent is capable of selectivelyremoving nitric oxide from mainstream tobacco smoke. Any conventional ormodified method of making cigarette filters may be used to incorporatethe activated carbon sorbent in the cigarette.

Embodiments of methods for making cigarettes comprise placing a paperwrapper around a tobacco column to form a tobacco rod, and attaching acigarette filter to the tobacco rod to form the cigarette. The cigarettefilter and/or tobacco rod contains the activated carbon sorbent.

Any suitable technique for cigarette manufacture may be used toincorporate the activated carbon sorbent. The resulting cigarettes canbe manufactured to any desired specification using standard or modifiedcigarette making techniques and equipment. The cigarettes may typicallyrange from about 50 mm to about 120 mm in length.

Other preferred embodiments relate to methods of treating mainstreamtobacco smoke, which involve heating or lighting the cigarette to formsmoke and drawing the smoke through the cigarette, such that theactivated carbon sorbent removes nitric oxide from mainstream smoke.

“Smoking” of a cigarette means the heating or combustion of thecigarette to form tobacco smoke. Generally, smoking of a traditionalcigarette involves lighting one end of the cigarette and drawing thecigarette smoke through the mouth end of the cigarette, while thetobacco contained in the tobacco rod undergoes a combustion reaction.However, a non-traditional cigarette may be smoked by heating thecigarette using an electrical heater, as described, for example, in anyone of commonly-assigned

U.S. Pat. Nos. 6,053,176; 5,934,289; 5,591,368 and 5,322,075, each ofwhich is incorporated herein by reference in its entirety.

FIG. 1 shows a preferred embodiment of a cigarette 10 comprising atobacco rod 12 and a multi-component filter 14 attached to the rod withtipping paper 16. The filter 14 has a plug-space-plug construction withspaced apart plugs 18, 20, such as cellulose acetate plugs, and a cavity22 between the plugs 18, 20, which contain an activated carbon sorbent24. In the embodiment, the activated carbon sorbent 24 is sphericalbeaded activated carbon. Other filter configurations can also beprovided.

In a preferred embodiment, the beaded activated carbon sorbent 24 cancomprise individual beads of a substantially uniform diameter. Suchbeads can form a bed that allows for minimal channeling of tobacco smokedrawn through the cavity 22. Accordingly, maximum contact can beachieved between mainstream cigarette smoke and the surface of the beadsfor efficient removal of NO from the smoke.

In another preferred embodiment, the filter cavity 22 can be filled withspherical carbon beads of at least two different size fractions.Smaller-size beads can pack uniformly between larger beads. For example,FIG. 2 shows a filter cavity 22 containing a combination of large beads26 and smaller beads 28 packed uniformly between the larger beads.

EXAMPLE 1

Activated carbon beads were produced by activating as-received, porouscarbon beads (molecular sieves) to modify the pore structure of thebeads. The as-received beads had a BET surface area of less than 1000m²/g. Comparing the D-R micropore volume of the pores sized from 5 Å to10 Å (i.e., 0.16 g/cm³) to the value of the pores sized from 10 Å to 20Å (i.e., 0.006 g/cm³) shows that the as-received beads contained a largepercentage of pores sized from 5 Å to 10 Å.

The as-received carbon beads were activated in an environment containingCO₂ flowed at a flow rate of 0.3 L/min and N₂ flowed at a flow rate of0.7 L/min and at a temperature of about 950EC for different time periodsranging up to 270 minutes. The activation results are shown in Table 1.

An NO removal test was conducted at room temperature for the as-receivedbeads and the activated beads. The influent gas mixture contained 500ppm NO, 10% O₂ and the balance helium. The gas mixture was flowedthrough the beads at a flow rate of 0.5 L/min. About 200 mg of theas-received beads and 200 mg of the activated beads were separately usedin the testing.

TABLE 1 D-R D-R Micropore Micropore NO NO BET Volume Volume RemovalRemoval Activation Surface of Pores of Pores After After Time % Area5-10 Å 10-20 Å Saturation Saturation Test (min) Burn-Off (m²/g) (cm³/g)(cm³/g) (ppm) (%) A 0 0 980 0.16 0.006 150 30 B 45 12 1040 0.19 0.03 27054 C 90 19 1370 0.31 0.14 310 62 D 180 33 1710 0.26 0.33 270 54 E 270 492430 0.20 0.61 230 46

As shown in Table 1, the % burn-off increased with increasing activationtime at the activation temperature. In addition, the BET surface area ofthe activated carbon beads increased from under 1000 m²/g (Test A) toabout 2500 m²/g (Test E). The D-R micropore volume of the microporeshaving a size of from about 5 Å to about 10 Å ranged from 0.16 cm³/g(Test A) to 0.31 cm³/g (Test C), while the D-R micropore volume of themicropores having a size of from about 10 Å to about 20 Å ranged from0.006 (Test A) to 0.61 cm³/g (Test E). As compared to a burn-off time of90 minutes, the D-R micropore volume of the micropores having a size offrom about 5 Å to about 10 Å decreased, while that of the microporeshaving a size of from about 10 Å to about 20 Å increased, for the higherburn-off times of 180 minutes and 270 minutes, demonstrating thatsmaller pores grew in size with increased burn-off time.

The results in Table 1 show that NO removal from the influent washighest for a burn-off time of 90 minutes. At higher burn-off times, NOremoval from the influent gas mixture decreased. It is believed thatthat NO removal decreased due to the reduction in smaller pores relativeto larger pores resulting from the longer activation times.

FIG. 3 shows the NO concentration (curve A) and the NO₂ concentration(curve B) of an effluent gas using the as-received porous carbon beads,and the NO₂ concentration (curve C) of an effluent gas using theactivated carbon beads activated for 90 minutes. The influent was an NO,O₂ and helium gas mixture. As shown in curve B for the as-receivedbeads, the NO₂ value initially increased to a value of about 60 ppm, andthen remained at about this value for the duration of the test.

While not wishing to be bound by any particular theory, it is believedthat the micropores of the as-received beads initially removed NO fromthe influent by adsorption until they became saturated after about 60 to120 minutes of testing. It is believed that the saturated as-receivedbeads acted predominately as a catalyst for the conversion of NO to NO₂for the remainder of testing. As shown in curve C, the activated carbonwas more effective than the as-received beads for initially removing NOby adsorption and also for catalyzing the conversion of NO to NO₂.

EXAMPLE 2

Tests were conducted to demonstrate the NO removal efficiency of carbonderived from coconut shells. Carbon derived from coconut shells having aD-R micropore volume for those pores sized from about 5 Å to about 10 Åof 0.18 cm³/g, a D-R micropore volume for those pores sized from about10 Å to about 20 Å of 0.28 cm³/g, a BET surface area of about 1600 m²/g,and an ash content of about 2.5%, were tested in the as-received state,and also after being treated at a temperature of 650° C. using a CO₂flow of 0.2 L/min. for a period of 5 minutes. The treatment wasconducted to modify the surface state of the carbon and enhance the NOadsorption capability of the carbon. About 200 mg of the as-receivedcarbon and the treated carbon were separately used for testing.

FIG. 4 shows curves of NO removal (%) versus time for the as-receivedcarbon derived from coconut shells (curve A) and the treated carbonderived from coconut shells (curve B). The test results show that thetreated carbon removed over 80% of the NO in the influent in the firstminutes, while the as-received carbon removed a smaller percentage ofthe NO. Both the as-received and treated carbon reached a plateau, whichis believed to signify that the micropores became saturated and thecarbon subsequently acted predominately as a catalyst for the conversionof NO to NO₂.

EXAMPLE 3

Tests were conducted to demonstrate the NO removal efficiency ofmicro-porous carbon derived from coconut shells when used to filtercigarette smoke. A smoking test system 30 as shown in FIG. 5 was usedfor the testing. The smoking test system 30 includes a Cambridge pad 32,a smoking machine 34, a quartz tube 36 in which carbon 38 was placed, acarrier gas source 40, and a gas detector 42. A cigarette 44 wasinstalled on the Cambridge pad 32, and lit to produce mainstream smoke.The mainstream smoke flowed into the quartz tube 36 and then into thedetector 42, which analyzed the NO, CO and CO₂ content of the mainstreamsmoke.

FIG. 6 shows test results using as-received carbon derived from coconutshells and treated carbon derived from coconut shells, respectively.About 200 mg of the as-received carbon and about 200 mg of the treatedcarbon were placed in the quartz tube 36 for testing. In these figures,the change %=(test−control)/control·100). In the control, smoke passedthrough the quartz tube 36 without carbon.

As shown in FIG. 6, the as-received carbon provided an NO reduction fromthe mainstream smoke of only about 20%. In contrast, the treated carbonprovided a higher NO reduction from the mainstream smoke of from about40% to about 50%.

As shown in FIG. 7, the treated carbon derived from coconut shellsprovided an NO reduction from the mainstream smoke of at about 60% forthe first four puffs.

While the invention has been described in detail with reference topreferred embodiments thereof, it will be apparent to one skilled in theart that various changes can be made, and equivalents employed, withoutdeparting from the scope of the invention.

What is claimed is:
 1. A method of making a filter, comprising:activating a carbonaceous material to produce an activated carbonsorbent, wherein a majority of the pores of the activated carbon sorbenthave a pore size of less than about 30 Å, the activated carbon sorbentcontains pores having a D-R micropore volume of from about 0.2 cm³/g toabout 1.0 cm³/g in the pore size range of from about 5 Å to about 10 Å,and the activated carbon sorbent is capable of removing nitric oxidefrom mainstream tobacco smoke; and incorporating the activated carbonsorbent in a filter.
 2. The method of claim 1, wherein the carbonaceousmaterial is porous carbon beads and/or the filter is a cigarette filter.3. The method of claim 1, further comprising placing catalyst materialcapable of catalyzing the reaction of nitric oxide to N₂ and O₂ and/orto NO₂ in the filter.
 4. The method of claim 1, wherein the activatedcarbon sorbent removes the nitric oxide from the tobacco smoke bysorption.
 5. The method of claim 1, wherein the activated carbon sorbentcatalyzes the reaction of nitric oxide to N2 and O2 and/or to NO2. 6.The method of claim 1, wherein a majority of the pores of the activatedcarbon sorbent have a size of from about 5 Å to about 10 Å.
 7. Themethod of claim 1, wherein the activated carbon sorbent has a BETsurface area of from about 1000 m²/g to about 3,000 m²/g.
 8. A method oftreating mainstream tobacco smoke produced by a cigarette including acigarette filter comprising an activated carbon sorbent, wherein theactivated carbon sorbent is produced by heating a porous carbon materialin an oxygen-containing environment under conditions effective toenhance the capability of the carbon material to remove nitric oxidefrom mainstream tobacco smoke by sorption, wherein the activated carbonsorbent contains pores having a pore size of from about 5 Å to about 10Å and has a BET surface area of from about 1000 m²/g to about 2,000m²/g, the method comprising heating or lighting the cigarette to formsmoke, and drawing the smoke through the cigarette, the activated carbonsorbent removing nitric oxide from mainstream tobacco smoke.
 9. Themethod of claim 8, wherein the activated carbon sorbent removes thenitric oxide from the gas stream by sorption.
 10. The method of claim 8,wherein the activated carbon sorbent catalyzes the reaction of nitricoxide to N₂ and O₂ and/or to NO₂.
 11. The method of claim 8, wherein amajority of the pores of the activated carbon sorbent have a size offrom about 5 Å to about 10 Å.
 12. The method of claim 8, wherein theactivated carbon sorbent has a BET surface area of from about 1000 m²/gto about 3,000 m²/g.
 13. A method of treating a gas stream containingnitric oxide, comprising: passing a gas stream containing nitric oxidethrough an activated carbon sorbent to remove nitric oxide from the gasstream, wherein a majority of the pores of the activated carbon sorbenthave a size of less than about 30 Å, the activated carbon sorbentcontains pores having a D-R micropore volume of from about 0.2 cm³/g toabout 1.0 cm³/g in the pore size range of from about 5 Å to about 10 Å.14. The method of claim 13, wherein the activated carbon sorbent removesthe nitric oxide from the gas stream by sorption.
 15. The method ofclaim 13, wherein the activated carbon sorbent catalyzes the reaction ofnitric oxide to N₂ and O₂ and/or to NO₂.
 16. The method of claim 13,wherein a majority of the pores of the activated carbon sorbent have asize of from about 5 Å to about 10 Å.
 17. The method of claim 13,wherein the activated carbon sorbent has a BET surface area of fromabout 1000 m²/g to about 3,000 m²/g.
 18. A method of treating a gasstream containing nitric oxide, comprising: passing a gas streamcontaining nitric oxide through an activated carbon sorbent to removenitric oxide from the gas stream, wherein the activated carbon sorbentis produced by heating a porous carbon material in an oxygen-containingenvironment under conditions effective to enhance the capability of thecarbon material to remove nitric oxide from mainstream tobacco smoke bysorption, wherein the activated carbon sorbent contains pores having apore size of from about 5 Å to about 10 Å and has a BET surface area offrom about 1000 m²/g to about 2,000 m²/g.
 19. The method of claim 18,wherein the activated carbon sorbent removes the nitric oxide from thegas stream by sorption.
 20. The method of claim 10, wherein theactivated carbon sorbent catalyzes the reaction of nitric oxide to N₂and O₂ and/or to NO₂.